We propose to study cell junctions in the ocular lenses of rat, rabbit and frog. The specific aims of the research plan include: (1) A comperative study of the structural characteristics and distribution pattern of gap junctions in normal lens fiber of rat, rabbit and frog; (2) study possible structural alterations of lens fiber gap junctions associated with the development and reversal of galactose cataract in the rat; (3) a comparative study of the structural characteristics of gap junctions in normal lens epithelia of rat, rabbit and frog; (4) study whether differences occur in the structure of epithelial gap junctions during the development and reversal of galactose cataract in the rat; (5) study formation pattern of gap junctions in the zone of differentiating epithelium during development and reversal of galactose cataracts; (6) study the structural characteristics and physiological permeability of zonulae occludentes (tight junctions) in the lens epithelia of frog, rat and rabbit; (7) determine the changes in gap junction structure related to the activation of cell division and growth of epithelial cells by serum in rabbit lens organ culture. Methodology involved will be as follows: Freeze-fracture TEM (conventional and rapid freezing techniques), light and electron microscopy; injection and incubation of hemeprotein tracers, cytochemistry, and organ culture techniques etc. The overall significance of the investigation is that it may: (1) provide a better understanding of the structural characteristics of gap junctions and zonulae accludentes (tight junctions), and physiological permeability of zonulae occludentes in lenses of various species, (2) show possible changes in gap junctions that are related to cataractogenesis, (3) determine the possible role of gap junctions in the control of cell proliferation and growth of the rabbit lens epithelium in organ culture.